Be more accurate with field name when referencing shared field, make re-usable API to list shared locations

Problem/Motivation

On the global field settings tab for a field it says, for example: "These settings apply to the Other tags field everywhere it is used. These settings impact the way that data is stored in the database and cannot be changed once data has been created."

The first part of that text says "everywhere it is used". It's difficult to know where a field is re-used/shared. Perhaps people get used to seeing that warning, and just proceed to change their settings even when they might regret it.

Also, it uses the Label for that field, which is unique to the field instance. So it could be interpretted as: oh, I only have one field called Other tags. My other tags field is called Tags, so I'm ok to change things here.

Proposed resolution

Be specific about where the field is shared and use the machine name instead/in addition to the Label.

For example:
"These settings apply to the field_tags field everywhere it is used: Other tags in Basic page, Tags in Article. These settings impact the way that data is stored in the database and cannot be changed once data has been created."

Remaining tasks

• discuss approach
• Implement the change, provide patch
• review patch
• rinse and repeat
• A screenshot with the fix would be nice.

User interface changes

Yes. See above to improve text of global field settings tab.

API changes

Making a re-usable API to get a list of places a field is shared seems helpful.

Related issues

• #1188388: Entity translation UI in core (find specific comment or follow-up issue number that discusses warning about what fields/bundles/entities/content types will be effected by enabling or disabling translation)
• #1854056: Handle shared fields in translation settings
• #552604: Adding new fields leads to a confusing "Field settings" form